Vertebrate in vivo models using aquatic species will enhance detection of potential health hazards associated with toxic waste sites since spread of contaminants may occur as ground water leachates, particulate emissions and surface water runoff. The overall objective of this research is to integrate conventional aquatic toxicity approaches with state of the art methodologies to establish biomarkers of response to toxic components of complex waste mixtures. Assays will include endpoints of mutagenicity, carcinogenicity, and developmental toxicity. Fish are proven environmental sentinels and studies in this laboratory have established the medaka (Oryzias latipes), a small aquarium teleost fish, as an in vivo model for first screening toxicity of chemical- contaminant mixtures isolated from soil, water and air at toxic waste sites. Economy, speed, and adaptability to fresh, brackish and near shore marine salinities enable modeling of site-specific conditions. Being small, medaka permit histopathologic sampling of all target organs at once and increase statistical precision through use of large numbers, and enable thorough sampling for stereologic assessment. This model is particularly well adapted for a toxicity-based approach to characterization of sites, prioritization of locales within a site, monitoring of bioremediation, and identification of toxic compounds. Use of specific life stages further characterizes host response; the transparent chorion enables noninvasive assessment of developmental processes, dechorionation ensures accurate timing of exposure and sensitivity, hatchling acute toxicity tests are first and detect effects of exposure on normal and abnormal (tumorigenesis) growth. To achieve the overall goal, 4 specific aims are proposed: 1) determine genotoxicity including hepatocarcinogenicity of specific sediment extracts from estuarine and coastal habitats, particularly those near military bases in California; 2) conduct toxicity assays on complex mixtures and, on toxic fractions, use rapid IAA followed by HPLC and GLC MS to identify toxic components; 3) use the medaka cDNA library, prepared in a phagemid, to screen for specific oncogene (ras) and suppressor gene (p53) mutations as well as for up and/or down regulations of specific enzymes which are indicators of response to toxic compounds; and 4) transfer technology obtained from superfund basic research to county, state and federal employees providing them with the tools and skills needed to self monitor specific sites.